1. Field of the Invention
The invention relates to a power supply unit and a light emitting apparatus. More particularly, the invention relates to a power supply unit and a light emitting apparatus with a dimming function.
2. Description of Related Art
Currently, the light emitting brightness and efficiency of the LEDs are continuously improved, and meanwhile the white LEDs with high brightness are successfully put into mass production, so the white LEDs have been gradually used in illumination devices such as indoor illumination and outdoor street lamp. However, as for the outdoor street lamps, the LED street lamps are generally designed to have a simple illumination function instead of bringing other added values to environment protection.
Specifically, many street light installations may provide nighttime dimming by a second phase. The second phase runs an additional light source that can be turned on or turned off independently, as shown in FIG. 1. FIG. 1 shows a schematic view of a conventional street light installation 100. Referring to FIG. 1, a power system 110 of the street light installation 100 provides signals N, L1, L2, and FG to power supply units 120 and 130. The power supply units 120 and 130 drives street light panels 122 and 132 to emit light after receiving the signals N, L1, L2, and FG. In such a configuration of the street light installation 100, when the power supply unit 122 is turned off by the signals N, L1, and FG, the street light panel 122 is turned off. Similarly, when the power supply unit 132 is turned off by the signals N, L2, and FG, the street light panel 132 is turned off. Furthermore, when the power supply unit 122 and 132 are both turned on, both of the street light panels 122 and 132 are turned on. On the contrary, when the power supply unit 122 and 132 are both turned off, there will be no light output of the street light installation 100.
Accordingly, the conventional street light installation simply has two modes, turn-on or turn-off. This will cause a lot of restrictions for applications, and energy is used more than is necessary.